This invention relates to protective apparel comprising an energy impact absorbing polymeric material and method for shaping the material.
Manufacturers and designers of protective gear and apparel are always striving to develop a product which provides the maximum amount of protection for the least amount of cost while optimizing fit and flexibility of movement. With regard to impact protective gear and apparel, such as bullet-proof (ballistic) vests or elbow or shin guards, the rigid surface material on the outer surface of such gear or apparel does not absorb the major force of the impact. The energy of impact is transferred through the rigid material and is passed through to the underlying material and subsequently to the body, causing bruising or impact trauma. In the case of body armor, such as bullet-proof (ballistic) vests, multiple layers of Kevlar(copyright) and Spectra(copyright) woven fabric are typically encased within a fabric shell and are collectively referred to as a xe2x80x9cballistic packxe2x80x9d. As a bullet leaves the barrel of a rifle or pistol, it not only has a high rate of forward velocity, it also spinning at a high rate of speed due to the rifling of the barrel. As the bullet enters the Kevlar, it becomes entangled in the Kevlar fibers and its forward motion is stopped. Allow this action prevents the bullet from penetrating the body, it does not dampen or absorb the transfer energy of the impact. It is this transferred energy that causes bruising and impact trauma in and around the area of impact.
In an effort to reduce impact trauma, trauma packs are used in conjunction with the ballistic packs. These trauma packs are typically constructed from the same Kevlar(copyright) or Spectra(copyright) fabric used in the ballistic packs but are made up of layers which are thinner than the layers in the ballistic packs. The thinner layers in the trauma pack are either laminated together or saturated to hold them together. However, these trauma packs add substantial weight, decrease the flexibility of the vest and, thus, the movement of the wearer.
With regard to other types supporting and cushioning apparel and protective gear, at present, foam pads are generally the primary means utilized by manufacturers to reduce injury. However, foam merely flattens directly under the point of pressure and does not redirect the pressure or energy of the impact. Although foam acts as a shock absorber, it is incapable of acting as an energy absorber. Foam does not flow or conform to specific shapes. Foam merely compresses and flattens under an external load. Using foam as a cushioning material and to merely cover tender spots results in restricted circulation and does not reduce discomfort and bruising.
Shock absorbing materials such as foam compress so quickly under pressure that they are unable to absorb enough energy to significantly reduce impact trauma. Thixotropic liquids such as those described in U.S. Pat. No. 5,869,164 to Nickerson, which is a mixture of microspheres in oil and a thickener, are heavy in weight and, because they comprise a liquid medium, they are non-compressible and therefore behave like a supporting device and do not reduce trauma or provide impact protection. As such, although shock absorbers reduce the risk of surface injury, they do not significantly reduce injury to the underlying tissues because a substantial portion of the energy is transferred to the underlying tissues. Furthermore, such liquid based devices are subject to puncture and leaking and are difficult to manufacture because of their complex formulations.
In addition, although it is described in U.S. Pat. No. 5,869,164 that glass and plastic microspheres may be mixed with thixotropic liquids, the microspheres are merely suspended in the thixotropic liquid and thus are free to move around within the liquid. This freedom of movement allows the microspheres to be pushed to, and concentrated in, areas of the thixotropic liquids which are not subjected to pressure. Movement of the microspheres thus reduces the effectiveness, especially over extended periods of use, of thixotropic liquids.
Moreover, bonding agents, such as polyisobutylene polymers, which are typically used in such cushioning devices, are almost always non-liquid at room temperature because of the molecular weight, chemical composition and thermoplasticity. As such, before working with these polymers and to make them flowable, the temperature of these polymers must be raised to lower their viscosity.
Resilient, conforming materials comprising microspheres are also described in U.S. Pat. No. 4,252,910 to Schaefer. Specifically, Schaefer describes a material in which gas-filled microspheres are cohered to a mass by a bonding agent; wherein Schaefer""s microspheres consist of an elastic copolymer preferably of vinylidene chloride and/or vinyl chloride copolymerized with acrylonitrile. However, the formulations of Schaefer have such a high viscosity, a high moisture content and sticky nature make the resulting materials virtually impossible to handle and are useless for most applications. For example, Schaefer""s material is non-liquid at room temperature and, according to Schaefer, the user must warm his or her foot above normal body temperature to soften Schaefer""s material enough to take the shape of the user""s foot. Moreover, Schaefer teaches that his material must be at least at body temperature to be flowable. In addition, Schaefer""s material has a very high ratio of polymeric material to microspheres, namely, about 53:1. Furthermore, Schaefer is unable to substantially increase the number of microspheres per unit volume because of the high viscosity of Schaefer""s material. The low number of microspheres in Schaefer""s material severely limits the number of interstices per unit volume which, in turn, reduces the dilatency of Schaefer""s material.
A further disadvantage of polyamide and polyisobutylene synthetic polymers as a binding agent is that the resulting cohered mass of microspheres shows a high degree of compression set (low compression regain) which limits the mass"" usefulness. This is especially true when such materials are used in cushioning applications.
Furthermore, to date there are no previously known methods for processing materials such as Schaefer""s mass into predetermined shapes. Contrary to Schaefer""s disclosure, in practice, it is impractical to fill an envelope with Schaefer""s material, especially any type of film through which moisture vapor can be transmitted. Schaefer""s material has such a high moisture content that, if encapsulated in a film through which moisture can be transmitted, Schaefer""s material will lose moisture over time which will change the physical characteristics of Schaefer""s material. Schaefer""s material also cannot be rolled, pressed or extruded because Schaefer""s mass is too viscous, too sticky and has a very high resistance to pressure due to its dilatent characteristics. Schaefer""s mass will act as a cushion and will only conform to an externally applied pressure as long as the applied pressure is applied a slow, constant, low force rate.
Moreover, whenever welding or sealing plastic envelopes, it is important to ensure that the plastic film to be sealed is clean and free of contaminants, especially in the area to be sealed. When encasing flowable materials, such as Schaefer""s material, there is the added problem of containing the flowable material while the film is being sealed. Previously, the only possible way to encapsulate such materials was to drop the material into a pre-made envelope which is sealed on three sides and then sealing the entry side after the material is introduced. However, this method is impractical and does not sufficiently overcome all the problems, for example, the flowable, moist materials are heavy because they comprise water and/or oil, they leak, they often contain solvents which are flammable, they separate into solid and liquid phases, they are adversely affected by temperature (water freezed, oil thickens), they cannot be incorporated into a dual density construction with other padding materials such as foam, and they are capable of supporting bacterial growth because of their high moisture content.
It is therefore a primary object of this invention to provide protective gear and protective apparel comprising an impact energy absorbing, viscoelastic, polymeric material having low density and a shape adapted for use with the gear and apparel.
It is a further object of this invention to provide a cost-effective method for processing viscoelastic, polymeric material at room temperature into a predetermined shape.
It is further object of this invention to provide a method for preparing a continuous sheet of polymeric material, which is viscoelastic at room temperature, at any length, having a uniform thickness and width.
It is a further object of this invention to provide a in-line method for processing viscoelastic, polymeric material at room temperature into a predetermined shape.
It is a further object of this invention to provide protective apparel comprising an impact energy absorbing material which, at room temperature, conforms to the user""s body and compresses under pressure and yet is capable of substantial regain when the pressure is removed.
It is a further object of this invention to provide a vest-like device, such as a ballistic or bullet-proof vest, which can be worn about the torso, having one or more pockets integral with or at least partially fixed to the device which contain a viscoelastic, polymeric material capable of absorbing the impact energy of a bullet or other such ballistic material.
It is a further object of this invention to provide a vest-like device to which one or more pockets or overlays are attached in a manner which does not restrict the elasticity or flexibility of the device; wherein the pockets or overlays contain pads or cells comprising an impact energy absorbing, viscoelastic, polymeric material; and wherein the pads or cells may further comprise one or more of the following, bonded elastic microspheres, foam, gel, liquid, gas or other suitable cushioning materials.
It is a further object of this invention to provide a trauma pack, for use in conjunction with a ballistic pack, that is thinner, lighter, more flexible and less expensive than currently used trauma packs made from layers of aramid fibers and used in conjunction with ballistic packs.
The compressive material of the invention provides numerous advantages over currently available supporting, cushioning and protective materials adapted for use in protective gear and apparel. These advantages include, but are not limited to: improved flexibility; better regain (elasticity); better impact resistance because the material of the invention absorbs a greater amount of kinetic energy because the material comprises more microspheres per unit area; better dilatency than Nickerson""s dispersed microspheres which exhibit little to no dilatency; better dilatency than Schaefer""s material because the material of the invention comprises a high number of microspheres per unit volume which translates into a high number of interstices per unit volume which adds to the dilatent strength of the material; decreased backpressure because energy is displaced among a greater number of microspheres; and conformation and deformation properties which are not temperature dependent.
The method of the invention provides a cost-effective, in-line method for shaping and/or molding a polymeric material at room temperature. The method is the result of efforts to design a process which would enable the polymeric material of the invention to be processed into a predetermined shape. Extrusion methods are not feasible because the dilatent properties of the material require such a high degree of pressure, that a device capable of such high pressures would be cost prohibitive. The only previously known method for encapsulating or otherwise shaping highly viscoelastic polymers at room temperature is a manual filling operation whereby a mass of the material is dropped into an envelope or other containment device which can be subsequently sealed.
The preferred protective body apparel, of the invention, comprises: one or more foundation components adapted to be removably worn proximate one or more parts of the body; and one or more pads comprising, a polymeric material capable of absorbing impact energy, which comprises a plurality of microspheres and which is viscoelastic at room temperature, wherein one or more of the pads is carried by one or more of the foundation components. The polymeric material and the microspheres are preferably combined in a ratio of between about 10:1 to about 5:1 by dry weight; and more preferably combined in a ratio of about 7:1 by dry weight. The polymeric material preferably comprises an ester selected from a group consisting of triethylene glycol ester or methyl ester of partially hydrogenated rosin; and may further comprise polyisobutylene, gamma-aminopropyltriethoxysilane, and/or gamma-glycisoxypropyltrimethoxysilane. The microspheres preferably comprise polyacrylonitrile and polymethylmethacrylate, and may further comprise ethylene-vinyl acetate, vinylidene chloride, vinyl chloride and/or acrylonitrile, and combinations thereof having a moisture content of less than 5% by weight.
One or more of the foundation components may comprise one or more pockets adapted to support one or more of the pads; and/or one or more of the pads comprises one or more seam allowances through which the pad is stitched to one or more of the foundation components. One or more of the pads may be carried by one or more alternative or additional means for carrying including, but not limited to, Velcro(copyright), hook and eye, grommet, button, zipper and snap. Further, one or more of the foundation components comprises ballistic-proof armor, including, but not limited to a ballistic-proof vest.
The preferred method of the invention, for processing a dilatent, polymeric material, which is viscoelastic at room temperature and capable of compression regain, into one or more predetermined configurations, comprises the steps of: providing the polymeric material, which is viscoelastic at room temperature and capable of compression regain; introducing an amount of the polymeric material into a flexible sleeve; inserting and running the sleeve, into which the polymeric material is introduced, between one or more pairs of rollers, each roller having at least one outside surface which contacts the sleeve as the sleeve runs between the rollers, to form a sheet of the polymeric material, encased in the sleeve, having one or more surfaces which corresponds to the outside surfaces of one or more of the rollers; wherein the polymeric material preferably comprises a plurality of microspheres and wherein the polymeric material and the microspheres are preferably combined in a ratio of between about 10:1 to about 5:1 by dry weight, and more preferably in a ratio of about 7:1 by dry weight. The polymeric material may comprise an ester selected from a group consisting of triethylene glycol ester or methyl ester of partially hydrogenated rosin; and may further comprise polyisobutylene, gamma-aminopropyltriethoxysilane and/or gamma-glycisoxypropyltrimethoxysilane. The microspheres preferably comprise polyacrylonitrile and polymethylmethacrylate, and may further comprise ethylene-vinyl acetate, vinylidene chloride, vinyl chloride or acrylonitrile or combinations thereof having a moisture content of less than 5% by weight. The outside surface of at least one pair of the rollers is preferably substantially smooth to produce a sheet of the polymeric material wherein the one or more surfaces of the polymeric material, corresponding to the outside surfaces of the rollers, are substantially smooth.
The method may further comprise the steps of die cutting at least a portion of the sheet of the polymeric material into one or more shapes; encapsulating one or more of the shapes in one or more flexible film alone or in combination with other suitable materials, to produce an impact energy absorbing pad, comprising, a polymeric material which is viscoelastic at room temperature, comprises a plurality of microspheres, and has a predetermined configuration. The shapes may be encapsulated by introducing the shapes into one or more whole or partial capsules or between two or more films and sealing any openings, and/or by drawing or pressing the shapes into a film vacuum previously or simultaneously drawn or pressed into a mold.
The sleeve of the sheet may comprise a first thermoplastic material which is preferably flexible, and the method may further comprise the steps of, placing at least a portion of the sheet in contact with at least a portion of a foam material and a second thermoplastic material; and applying a means for causing at least a portion of the first thermoplastic material to adhere to at least a portion of the second thermoplastic material to capture at least a portion of the foam therebetween. The first and second thermoplastic materials preferably comprise polyvinyl chloride, polyurethane, polyolefins such as polyethylene or polypropylene, or other suitable flexible, thermoplastic film materials. The means for causing the first thermoplastic material to adhere to the second thermoplastic material preferably comprises radio frequency or sonic or impulse energy.
The method may also comprise the steps of, vacuum forming and/or drawing at least a portion of the second thermoplastic material into a mold; removing the sleeve from at least a portion of the sheet prior to the vacuum drawing step; die cutting a portion of the sheet, from which the sleeve was removed, to form one or more shapes; introducing one or more of the shapes into the mold with or without one or more layers of foam; and applying a means for adhering the sleeve to the second thermoplastic material, to produce an impact energy absorbing pad, comprising, a polymeric material which is viscoelastic at room temperature and a plurality of microspheres, and has a predetermined configuration.
It is envisioned that materials and methods of the invention may be adapted for any protective gear and apparel which is used to reduce the risk of trauma caused by pressure or sudden impacts. The materials and methods are envisioned for use with bullet-proof vests or jackets and other ballistic-protective gear and apparel; any type of protective clothing apparel used for riot control, corrections activities or apparel or equipment used in connection with martial arts; any type of apparel or article worn on or over any portion of a person or animal; protective gear, including, but not limited to, any type of helmet and shin and elbow guards; gloves; ski boots; snowboarding boots, motorcycle gear; all types of skates including, but not limited to, hockey skates, figure skates, racing skates and inline skates; all types of athletic footwear including, but not limited to, soccer, basketball, rugby, football, tennis, jogging, climbing, cycling; shoes; boots; any other type of footwear; any type of orthopedic cast or brace or the like.